Duplex radiotelephone system



y July 6, 1926. l

R. D.. DUNCAMJR DUPLEX RADIOTELEFHONE SYSTEM Filed July 24. 192,5 2 sheets-sheet 1 July 6,1926.

I v 15591,()25 -R. D. DUNCAN, JR

DUPLEX RADIOTELEPHONE SYSTEM.

Filled July 24. 1925 j `2 Sheets-Sheet 2 Patented July 6, 1923. u i. Y I f i i i i i f y UNITED fsrarsfear-surf @WEE- ROBERT D. DUNCAN, Jn.,- or EAs'rlonANeE, NEW JERSEY, AssrGNon To vri'mip narnia Y HINC., orv NEWfYonK, lN; Y., A CORPORATION or niiiiawanng Durnrix nAmoTnLErHoNE SYSTEM. i

Application file d''uly 24,51925'. Serial No. 45,948.-

telephon'y and more particularly toasystem V"nridgeV orflbalanced circuits `in'Which the of duplex radio telephony. Y etfect ofv the transmitting circuit'is neutral? vMyA invention relates'.broadlyftoy radio plicated and havev dependedllargely lupon y One of the objects of my invention is to ized or Vbalanced"inv so'far asV it acts upon 5v provideea system of radio ltelephonytinv the receiving` apparatus.' Due ftoy relatively which transmission and reception vmay be high powerfof.anormalhigh.frequencyradio1 carried on simultaneouslyWithout mechantelephonetransmitterand to the extreme'v ical switching means for rendering "the sensitivityot the receiving'-` equipment Withj transmitter inoperativey when receiving .and out such balancing circuits,y even 4with the 10 vi'ceversa`. Y

fnotherobjectof myinvention is to pro? 1fairly VWidely separated, 'the intense mag- 'vide a dupeX radio telephone lsystem `in netic and vstatic iiel'ds established by-f-the which simultaneous two Way communication transmitting current tend V.to paralyze the j may be conducted with closely related trans-YV receiving apparatus and render 'l itV prac- 15' in'i'tting yand' receiving antennae Withoutintically `impossible to simultaneously transl I terferencefifrom side talk inthe receiving `mitand receivefonthe same or onclosely system. 'adjiacent antennae;v

transmitting and receiving frequenciesV t Still another objectief my invention is .'By my. present-inventionIl pro'vide a I to provide l a polyphase system offradio three phase high frequency 'generating sys-, 10 transmission in which energy derived'V from tem With connections torA impressing` a poi` one of the phases-oi the vpolyhase system is ltion of the high frequency energy upcn a utilized to 'affect a local receiving ',circuitto radiating circuit. Thereceiving system'is* balance out the'disturbing intiuencesof the located closely adjacent` v` the transmitting transmitting system upon the local receiv-'j apparatus and a li'nlrcircuit'isprovided be ngeireut tween the 4transmitting system and Vthe re- A further object offmy .invention is to ceiving system for impressiiiguponthe rei l' provide a radio telephone system in WhichY ceiving system a-l portion of` the lhigh ,tra

simultaneous transmission andV reception on quency energy r`from the transmitting circuit. closely adjacent antennaer may befconducted The receiving system'has va normal voltage y iii: by means of the use of threephase highfreinduced -therein by direct action 'fromv the quency currents aty the transmitting appatransmitting antenna.A By virtue ofV the ratusl p .A

My invention Will be more clearly under?- phase system, the. high frequency energy peculiar phase relations existingin a three stood from the specification hereinafter folwhich 'is arbitrarily'introduced into the rel.

35 lowingv hy reference 4tol'thefaccompanying ceiving systemv from the transmitting sysl tem has its time' phase in direct opposition drawingsdn which: n y l Figure l is a VWiring diagram showing a to the time pliaseof the energy existing in transmittingfand'receiving stationembodythe receiving circuit by action. from'f'the ingvthe principles' of'gmy invention; Fig. 2 transmitting lcircuit as a result of -Which represents'at A, B, and() vector diagrams interfering currents in the receiving system otcurrent, magnetic flux and voltage, in the are neutralized and the receiving circuit Vcircuitsot the communication system; and l functions lwithout'l 'interference from the Fig; 3 illustrates a circuit diagram of a .local transmitting systemxkIn this manner complete duplex v or simultaneous two rvay simultaneous transmission and .receptionvv on 45' transinittingand receivingpsystem showing closely adjacent antenneevina-y'be conducted z i the 'application of my invention.

Heretofore 'ini the'fartduplex systems of V. tiveen the 'transmitting and receiving :ape radio telephonylon the'same or, on .closely paratus. u 'f Y vvithoutinechanical switching means'v beadjacent antennae `have been relativelyaoom- The advantagesv ot being able vtosimul-li" Y ll to ground B;

tov

Vand ll, the shield suitablepoint. lnductivelyr coupled With in-v Vductance l() is the receiving circuit 18, comfvr prism-,c5 inductance 19, capacity 20, aV-yacuum Y vence character 25 as of the seltairship, the vadditional advantages are mani fest.. Y' Y n Referring to Fig'. l ofthe drawingdlrferencecharacter l 1epresentsa source of' .modulated threeV phase Vhih frequency energy, 2, 3f, `l., indnct'ances shown tor example .connected in Y te each phase of the highV frequency source l. Reference numeral 5 designates tr "nsmitting antennar Connected inscriesbwith inductxfinces 16, 7, to ground 8.V nductancf-is 7, are shown jnductiVely coupled to inductances 2,3. Reference character shoes a receivingantenna connected inlseriesniith inductances l0 and r-nductively Ycoupled with inductances 4; and y 'l1 is series circuit Vl2 comprising inductance l3,rariable capacity 14, indnctance l5 and variable resistance 16. .This circuit isshown Vshielded xl7 from both the circuits containing inductances ltube detector circuit represented in its entirety by 2l 'andshown containingtelephone receivers 22, in the output circuit.V lnductancelO is shielded from inductance 19 by VVVmetallic shieldV 23, sho'wnlgrounded at 8.` ll/linie I vhave illustrated the inductance-s 2,

and d, as connected in Y it will he understood that the inductances may be connected in A. Theftransmitting antenna may be closely adjacent the receiving" antennai.

ln Fig. P) I harei .strated a complete cirjcuit diagram ot a d plex*transmitting and receivingv system. The three phase high freqi ncy current is developed for erample by a. circuit arrangement which more particula .11V described in my co-pendingl application Serial- Number 1,374, 'tiled January 5, 1925, Patent No. 1,578,88l. Rete-rence is made to myY fao-pending application. for a, complete deseriptionthe three phase high trequem cycurrent generator. For the Ypurpose ot clearly -eXpla', the operation et t .ne duplex system of the present application. it W- lllbe sulicient to'obserre that a. single Vphase high requenc7 current generator ot any suitable type, illustrated here by reiter- Y cited 'elem tron tube type, is connected as illustrrfrtedty reference character 48 to the tunedAV stem 26 which is coupled through the Y connected inductance Ysystem 27 ,as represented by brace l with electron tube high reqnencypower ampliefrs 2B, 2e, 30, the entri-,1t cilcuit-s of Which'impress polyphase high tre;-

beine Grounded at 8,;at aV placed intime phase by. l120".

' quency'signaling energy on the transmitting antenna system through couplingcoils 2-6 and 3 7. The coupled system 26 serres to set up a rotating high frequency magnetic field which is picled up bythe inductances 2T disposed at the proper angles 'with respect to coils 26 tor setting upV currents in coils 2T displaced in phase from each other by i200. VEnergy delivered from amplifier circuitS'O-jis impressed'iugen the link. circuitjl2 through coupling` coils 1t-i3 is in turn impressed upon the receiyingsystem through coupling coils lli-lli.. Modulation ot the system is secured through parallel connectec tubes 43, le and vl5controlled from micro-V phoneY connected in'Y theinpu't circuitof Vthe amplifier, the output of the tubes e3,

154, and' beingv connected across the. output circuits of each 'ofthe tubes V28', 29, and 30 liter. controlling vvthe Voutput tl'iereofwith1re-` Yse have the relationship as represented in Vector diagram A of Fig. 2 Where they are disf.

The Vectors are assumed to rotate in a'counter clockwise direction, Current l establishesV a magnetic field q5, shown yectorially iin-Fia'. 2

(B) .in-time phase vwith 1, and which links with inductances 2 and 6 as indie-ated by a dottedfline in Fig. l, Magnetic field es, induces a driving Voltage el? in inductance G. lagging in time phase as shown in Fig. 2 (B) by 90".V The antenna circuit is tuned to resonanceto theV frequency f T- yot the source l and the resulting current i@ Which ltends to flow under the action' ot' voltage @,T is substantially in phase `with k01T as shown in Fig. 2 The'same is true with the magnetic field ft2 linking'inductances 3, '7,

as shown in dotted line inlig. l, produced by current and in phase therewith, tending to cause the current izfr, '12Go lagging im. to flowV in VtheV antenna circuit. The resultant current 71T, which flows in Athe transmitting antenna 5 under tl'iecombined action of voltagesen` and agr, isthe `vector sum of. ,T and iw, which is shown inFig. 2

V(B) as the rector T lagging 1T by 60.

Reference is now made te Figi. A2 (C) ccn-Y sidercd in conjunction with Fig. 1 '.lhe i vresultant transmitting antenna current fz'T produces armagnetic leldqbT in phaSe with T and surrounding the antenna. This field mpnges'vupon the( :receiving enna 9, closely .adjacentto'the tra "fiittm .ant-hna, and induces therein div ng 'yo tage-axes' l therefore lag' @TR in time phase, shown vin lagging in time phase by substantially 90. Now the receivingjantenna circuit is adjustedl to resonance to the receiving fre-V quency fR which diifers'inl value from fT.

Fori-frequency fR thereactance ofl Vantenna 'circuitV 9 is'ctherefore substantially zero. f Forillustration it is here assumed that the transmittingy frequency fT is greater Athan the receiving frequency fR and hence at Ythis frequency antenna circuit 9 behaves as an inductive reactance.V The current which the voltage entends to cause toflowv will Fig.` 2 (C) .by the vectorc'fm llaggingeT'R by the angle 6; If fT were Vl'ess' .th'an fR,

currentiz'rq-R wouldlead VeT'R.y Now transmitl Vting current .-3 establishes magnetic'. fieldV 3 which does not act upon the antenna cir-v cuit 5, Vbut which links with inductance 13 of circuit 12 as shown infdotte'd lines in Ifig.

'1. It induces `in this inductancedriving;

voltage @lagging q5 by 90. By: means -of variable capacity 14, circuit 12is 'tuned substantially to resonance to Afrequency f1;

Yin which case the current 2. which flows will be approximately 1n 'phase withv e3.

Current 13 establishes magnetic fieldy (1513 Vin phase therewith, kwhich linksinductances 15 and 11 and induces in the latter, i. e., Ain the ,receiving rantenna circuit 9, driving voltage 613g. lThisvoltage is practically 180 out fof phasewith voltage eTRinduced directly'in the receiving antenna by the `transmitting antenna. Y The current which tendsl'to flow 'in circuit V9 .Y under theVV action of voltage e1 R will lav ela; bi Vthe an 'le 0` and is re 3- a c a 1.

Y resented by 113'R..Th e 'amplitude of 13R and hence 113B is regulatedby means of coupling between inductances A1c-18 and 1l- 15, andbylrvariation of capacity v14 and resistance 16, With the amplitude of @13R equal to that of'crn, and with its time phase v in opposition thereto, it will ybe observed' that vno current will flow inv receiving antenna circuit9due to current flowing` in transmitting antenna l5. Shielding of? the link circuit12 iand of lthe receiving circuit is desirable as it protects the circuits 1 so shielded from electrostatic effects of the transmitting current and enables the 'ob-1,

taining of more perfect elimination of all induced effects in thereceiving circuits. Y

By the methods and' circuits just' disclosed simultaneous radio telephonel transmission Vand rcceptionlon antennae close proximity Vof each other may tbe conducted" with suitable transmitting and" receiving f frequencies without either complete Vparalyzing'of the local receiving apparatus by the local transmitter orgivi'ngrrise to eX- c'essiye yand disturbing side tones. In fact' the absence of side tones may beso completey that the operator -will be unable t0 hear` any of his own conversation,` Which for' 'many reasonsis often an undesirable 'condition so lthat the balance `obtainedfat link circuit-lQ may be arbitrarily disturbed so -asto yield side tones jftlieV required intensity. v Y

Il haveillustrated-only one v'n'n'eth'od of modulation `;wh'ich ma`y be employed' in the transmitting system, but it willi beA understood that grid modulation or other arrangements of circuits-'may be yprovidedv for edect ing thetransmissionof signals. It will also Vbe understoodthat I may employ other ar- 5 r1While I 'have described' my invention in 'certain'particular embodiments, I desire that it 4be {nnderstood that vvmodifications ymay be madeandthat no limitations upon ythe invention are--in'tendedl otherthan those fimposedv by theY scope of the appended claims. i What I claimand' desire to secure byLet- 'ters I )jatentv ofthe UnitedV State'sfisV as fol- 1; AdupleX radio'transmissionand receptionfsy'stem comprising infcombination source of three phase high frequency electrimeans for exciting-said antenna system with twophases of .said-Y source,a receiving system and Aconnectionsv between,V the remaining phase of lsaid source of high frequency energy and said receiving system for impressing thehigh frequency electrical energy of ,said remaining `phaseV Vupon said `receiving system'for neutralizing the effects of the. 'transmitting system upon saidl receiving' EQ/YSteI-Il' v i l i i .tv` 2, A duplex Vradio telephone transmission 'cal enfergyn' a transmittingfantenna system,"

and reception system comprising` in combinat-ion f a 'source of `modulated;three' lphase lngh frequency electrical energy, a transmit- `tingantenna system, means for exciting said antenna system with two phases of said source, a .receiving'system and connections between saidA source o f high frequency energy' and said receiving system for impressing the high frequency electricalenergy from the ren'aaining fv phase of saidvsource*y upon said `receiying system for lneutralizing the effects ofjthe resultant vcurrent derived from the' first 'mentioned two phases of said source. i

3. radio telephone communication system comprising Vincombination al transmitting andrec'eifving system vin close proximity l'oeach other, azsource ofthree'phase'electri- V` ral energy, means for-#impressing energy from v two phases of fsaid three phase source upon said transmittingjsystem. and means fonimpre'ssing'energy from' vthe third rc mailling-phase of said source Aupon said re-v ceiving` system for v-neutrali'z ing the eects in Said recevingsystsm'or" the high Ifre- .que-ncy electrical energy transmitted by said Y transmitting system.

. 4. A r adio communicationsystem tor duf plex operation comprisingin combination a transmittingricircint, a receivingcircuit, a"

ysource ot tliree phase high-frequency electrical energy, means for impressing two phases of said energy on said transmitting circuit, and means tor impressing the remaining phase' of said electrical energy upon said [receiving circuit for balancing the ei'ects vtherein otthevectorsum ot currents derived :from said transmitting circuit.V

5. A radio communication system comprising in combinat ion'aV transmitting circuit,

a v,receiving circuit'Vv located in f Proximity thereto, a souice'ot three phase' high .treqriency, electrical energy, means for impre. i fit-ivo phases of said energy'upon said f ransi-nitting circuit, and'separate means 'tor impressing the remaining phase ot said enf .orgy uponV s-aidreceiving circuit tor establishing in said receiving circuit current having its time phase in opposition to the vector sum ot' currents existent in said receiving circuit by reason ofthe inliuence ot Vsaid transmitting circuit upon said receiving cir- 6. A duplex radio transmission and reception system comprising in combination a vsource of three phase high frequency' electrical energy, a transmitting system, means for Vexciting said transmitting system with two .phases ot said energy, a receiving system, a linkcircuitinterconnecting the other Vof the phases ot vsaid source with said receiving VV-syst-emtor impressing high frequency electi-ical' current upon said receiving system in phase'opposition to theV vector sum of currents otherwise existenttherein from said first mentioned two phases tor neutralizing the ett'ectsv ot the transmitting system upon said receiving system'.

7; A radio telephone transmitting and recciving system comprising in combination, arsource of modulated three phase high frequency .c;ur'rent,` at least one inductance elecv trically Vassociated With each phase of said source and interconnected in a three phase manner, a transmitting antenna system containing a plurality of inductanccsitwo ot vsaidlast named inductances being induc-y Vtively coupled independently' with tivo et saidV iirst na-med i'nd-uctances, .a receiving antenna system in proximity to 'said train;mit-

ting antenna system, a yplurali-ty of inducf 'Y ftanees in series connection Witliisaid receiv` antenna, ra signal t sponsiye means ass ted W li one of lsaid receiving antenna. indetta es, a link @ir- -eui-t containing at least two inductances -in seriesconnection, one :of said mailling of said three first y.menticned inlating and .re- Y l ircuity inclemencias iat-uctrvely emailed A.0 the teductances, the remaining lof said link circuit inductances inductively coupled VWith ref v maining ot' said tivo lreceivingy antenna inductances, the adjustment of said transmitT tingv and receiving antenna systems `in con?- binatioii with that ot said'linl: circuit v by virtue-ot 4the opposing vphase relations ot the voltaoes established in said 'receivingV antenna system by the currentinlsaidtrans# Vmittingantenna and through the means ot ysaid link circuit providing a means et -e't- `iccting simultaneous transmission and recepvtionWithout the said signal translatingandY responsive means being rendered inoperative or its sensitivity substantially inliuenced 'from .the induced Veliects in L saidv vreceiving antenna system caused by current existent in said transmittingantenna system;` p

8. A radiotelephone transmitting and re# ceiving system comprising Ain combination afsource of. three phase'highi'requency current, a plurality et electron tube circuits nr.corresponding in number tothe number oit Vphases ot said source, an inputcircuittor each of said electron tube circuits, in duc.

tancesrin' each ot said input circuits electrically associated with `each phase ot said Vthree phase source, an output circuit tor cachot said electron tube circuits, said out- ,put circuits each containing'an inductance, a transmitting antenna system inductive'ly coupled to two of said outputinductances, means tor effecting telephonie modulation ot"` the-high frequency energy existent in said electron-tube circuits, a Vreceiving tenna system lin proximity Vto said transmitting antenna system and ,containing a plurality otinductances, afsignal translat-V fing and responsive means electrically associated with one ot said'last mentioned inductances, a link circuit'conta'ining Va plurality of inductances, Vsaid linlr circuit' inductively coupled to the third of said output inductances of said electron tubecircuits and to the other et said plurality ot vadjnstn ient .of said transmitting and ie'ceivT eo Y 11o receiving' antenna system inductances, the

ing antenna systems and of said linlr circuit by virtue oi the opposing 'phase .relations ot the voltages established in said receiving antenna system lby the vcurrent inL said transmitting antenna. and through the means ot said link circuit providing a means ot et feet-ing simultaneous transmission and reception Without said signal translating and responsive means being'rendered inoperative lng energy frorntwo phases ofsaicl three phase source upony said transmitting` an- :tenna system, means for impressing energy `from the. thircl remaining phase of saicl` souiee upon said receiving system `for neutralizing the effects" in saldrecelving antenna system of the high frequencyy electrical energy transmitted. by said transniitV ting antenna system, and means interposed loetween said three phase lsource and said 10.l 

